ALLENTOWN, Pa. — Daniel Klem Jr. cradles a small, dead bird with chestnut-mottled wings, another victim of what he says is a largely unrecognized environmental hazard that kills birds in flight.

The culprit is the plate glass used in windows, skyscrapers and other structures, which the birds strike because they cannot see it.

“Glass is ubiquitous and it’s indiscriminate, killing the fit and the unfit,” said Klem, a Muhlenberg College ornithologist who estimates that collisions with glass kill up to 1 billion birds a year in the United States alone.

“Buildings that we have created to be aesthetically pleasing are slaughtering birds.”

Second only to habitat destructionAlthough cell phone towers, oil spills and power lines raise the ire of conservation groups, those hazards pale in comparison to glass, Klem said. He estimates that only habitat destruction kills more birds.

When glass is clear, birds see only what’s on the other side; when it is reflective, birds see only reflected sky and trees. Either way, they have little chance of survival.

Despite three decades of work and research, Klem has had a hard time getting people in the conservation community and the building industry to hear his call.

Klem has monitored houses and commercial buildings and counted the number of dead birds, then compared the collision rates of plain glass to glass altered with visible patterns so it’s not strictly clear or reflective.

He has monitored glass-skinned skyscrapers that he says kill 200 birds every day and suburban dwellings that he said are just as lethal when taken in total. And he says that glass-walled structures abound even in places that rejoice in wildlife — from Central and South American ecotourism sites to Pennsylvania wildlife refuges.

“If what I’ve found out over the last 30 years is true, then it’s not going to get better, it’s going to increase,” he said. “Whether people ignore me or not, it doesn’t change that.”

Awareness slowly takes hold
His work is starting to get some recognition.

“This is a largely unseen but seriously unappreciated phenomenon and we’re starting to take a serious look at it,” said Frank Gill, chief scientist for the National Audubon Society.

Carr Everbach, a Swarthmore College engineer heading a “green team” working on a new science center at the school, likens plate glass to other scientific advancements later found to harm the environment, such as ozone-depleting CFCs and leaded gasoline.

Carr Everbach, a Swarthmore College engineer, observes the window glazing at the school's new science building. Patterned plate glass is both visually attractive and visible to birds to deter them from crashing into it.

The new science center will have glass etched with dots and other patterns, which the green team hopes birds will see and avoid. The building also will have clear glass and “thump sensors” to see if — and where — birds strike the structure.

A new observation tower at Niagara Falls State Park also was designed with birds in mind. Original plans called for reflective glass but after architects and park officials were told of Klem’s work, glass with a stripe pattern was used, said Thomas Lyons, New York State Office of Parks’ director of environmental management.

It’s not clear whether these efforts will save birds. But Klem said he’s heartened about the new interest in bird-friendly buildings.

“The heart of this is to get a piece of glass that will solve this problem. We can’t say that we have that yet,” he said. “But I’m more encouraged than ever that we can come up with a solution that will stop this senseless slaughter of wildlife.”